It is known to provide a sprinkler head having a valve member retained in a closed position by a latch means. It is known to provide a temperature responsive means for releasing such a latch means. It is desirable to use a bulb of glass or other frangible material and containing a temperature responsive fluid as the temperature responsive means. In order for such a bulb to be sensitive, it has heretofore been thought necessary that the bulb have very thin walls. Since the bulb is used as a latch retainer, the fluid system pressure imposes a practical limit on how small and thin-walled the bulb can be. The present invention provides a solution to this seeming impasse.
In copending application U.S. Pat. No. 4,619,327, there is disclosed a solution of the problem of how to reduce compressive pre-load on the bulb whereby the bulb may be smaller and thinner than prior art bulbs. Copending application U.S. Pat. No. 4,609,047 discloses three-sided, non-uniform-thickness bulbs designed to achieve improved sensitivity. The present invention is directed to a solution of the problem of how to produce a small, thin-walled bulb having a configuration which will cause the bulb to rupture more quickly than prior art bulbs while retaining the ability of the bulb to resist compressive forces.